1. Field of the Invention
The invention relates to the field of the observation and formation of images in an infrared radiation band and is aimed, more particularly, at a self-checked optronic system for observation in such a band.
Optronic systems such as these, mounted on board an aircraft, carry out angular tracking by passive day-and-night imaging, respectively using Vidicon or TV type tubes for visible radiation and FLIR (forward looking infra-red) type tubes for infra-red radiation.
This imaging makes it possible to supply servo-mechanisms for positional servo-control with information on angular deviation between the direction of the target and the direction of the sighting axis. In optronic systems for target designation by laser beam guidance, the direction of the sighting axis is furthermore indistinguishable from the laser illumination axis, the target being then illuminated with precision by the laser.
The invention, which can be applied to any optronic system of infra-red observation, is described more precisely and illustrated in application to an optronic laser designation pod with several optical channels.
2. Description of the Related Art
As shown schematically in FIG. 1, the opto-mechanical structure of a standard laser designation pods typically includes a multi-spectral input port 1 and a common optical channel defined by a first gyro-stabilized optical head system 2, for example a Cassegrain type assembly as shown, to provide for a angular range of shift in two axes (relative bearing/elevation), and a second image-offset system with 3, 4 or 5 mirrors, to keep the final position of the center of the image in a plane of detection. The separation of the infrared/visible/laser channels takes place only subsequently, by means of separators M1 and M2. If necessary, there may be a laser telemetry channel. The sighting beam from the laser L, represented by a double-headed arrow in FIG. 1, is collimated by means of an adapter 4 before being directed to the common optical channel. The incident observation beam, represented by a single-headed arrow, is analyzed by being focused on the thermal camera CT, the tube T and, as the case may be, the laser telemeter TL, after separation (mirrors M1, M2 and M3) and focusing (lenses L1, L2 and L3) respectively on the infra-red, visible and laser channels.
This type of optical-mechanical-optronic structure, which is found for example in the patents Nos. FR 84 16033 or U.S. Pat. No. 3,854,821, is conveyed in a frame configured in the form of a cylindrical pod mounted beneath the aircraft.
Other pods with separate optical channels have also been made, each channel having a port, an optical head system and an image offset optical system.